Bluetooth 1.2 specification—introducing, among other feature, Adaptive Frequency Hopping (AFH), which is designed to reduce interference between wireless technologies sharing the 2.4 GHz spectrum—has been officially adopted by the so-called Bluetooth Special Interest Group (SIG). However, the Bluetooth SIG continues its work to improve Bluetooth. There are several possible improvements under discussion, including ideas in connection with QoS (quality of service), scatterneting, and connection setup.
In Bluetooth, before any two devices can connect to each other and so communicate with each other, the two devices must go through a device discovery procedure, which, in case of a first device attempting to connect to another device whose address is unknown to the first device, includes two steps: inquiry and paging. The inquiry step/phase is for devices to find each other, while the paging step/phase is to establish actual connections. Any device can initiate a connection. The initiating device then becomes what is called the master. A connection is established by an INQUIRY message, which is followed by a subsequent PAGE message. In case the first device knows the address of the other device, a connection is initiated by a PAGE message.
In the inquiry process devices exchange data to perform actual connection set up (called paging). One of the improvement ideas is to extend the current inquiry procedure in such a way that more information can be sent out during the inquiry process, making it possible to connect to certain devices faster.
The basic idea of the enhanced inquiry process, as illustrated in FIG. 1, is that after an enhanced inquiry-scanning device/scanner 120 responds to an ID packet 11a from an enhanced inquiring device/inquirer 11 by providing an FHS (frequency hop synchronization) packet 12a—used for synchronizing the hop sequence of the communicating devices 110 120—the enhanced scanner 120 then sends out some predefined additional data 12b as an ACL (asynchronous communication link) packet, which could include service discovery and other device information. The additional data is sent on the same frequency as the FHS packet, so as not to collide with the ID packets if the inquirer is a legacy device. The enhanced inquirer 110 can then scan for the additional data and get further information regarding device identification and other properties of the device 120 providing the additional data; with the additional data, the enhanced inquirer can decide more quickly if the device 120 is the one the inquirer 11 is looking for, or offers the services or features the inquirer is looking for.
An enhanced inquirer uses the same ID packets as a non-enhanced/legacy inquirer. Also, an enhanced scanner uses the same FHS packets as a non-enhanced/legacy scanner. Hence, during the inquiry process neither the inquirer nor the scanner can know whether the other supports enhanced inquiry. Because of this, an enhanced scanner will send out the additional information even though the inquirer may not be able to read it. This causes some unnecessary interference in the ISM (industrial-scientific-medical) band in cases where the inquirer cannot read the additional data. FIG. 2 illustrates a case where a legacy inquirer 21 is in communication with an enhanced scanner 12, which transmits the additional data 12b in response to receiving an ID packet 11a from a legacy inquirer 12 since the enhanced scanner 12 cannot determine that the inquirer 12 is non-enhanced, and FIG. 3 illustrates the other case, where an enhanced inquirer searches for the additional data after an FHS packet, even though the scanner sending the FHS packet is a non-enhanced/legacy scanner and so has not transmitted the additional data.
The improvement idea for the inquiry process—i.e. the enhanced inquiry proposal—specifies that the enhanced inquirer only listens for the extra data for a few microseconds; if there is no additional data packet in that time period, it can restart sending ID packets immediately after the time period. However, it is not possible to start sending right after listening only a few microseconds, because the ID packet is transmitted on a different channel than the channel the inquiring device is tuned to for receiving the additional data. Therefore, the inquiring device misses the inquiry response packet if there is a scanner scanning the channel, because of waiting for the additional data.
Another proposal concerning connection setup is an enhanced paging proposal, illustrated in FIG. 9. The method modifies the normal paging procedure to enable devices to exchange small amounts of data without entering an actual connection state; it provides that a paging device 910, i.e. the device acting as master, can transmit any packet in place of an FHS packet. If a page scanning device 920, i.e. the device acting as slave, receives some other packet 91b instead of an FHS packet as the master response, it can then, according to the proposal, respond with any packet 92b. In this way the devices can each wirelessly send to the other a packet of information such as e.g. business cards. If, however, the page scanning device 920 receives an FHS packet (i.e. if the packet 91b is an FHS packet), a connection is set up in the normal way.
A problem like the one for enhanced inquiry occurs also for enhanced paging. If an enhanced paging procedure occurs after a normal inquiry procedure, and if the devices have not been connected before, the paging device does not know whether the page scanning device is capable of enhanced paging or not. As illustrated in FIG. 10, a legacy page-scanning device/slave 92 waits for the FHS packet as a master response. According to Bluetooth specification 1.2, and as shown in FIG. 10, the slave 92 listens as long as no FHS packet is received or until a pagerespTO (8 slots) timer indicates the waiting time is exceeded. If the legacy page-scanning device receives some other packet 91b, it continues to wait to receive an FHS packet. Therefore, the enhanced paging delays connection setup of a page scanning legacy device to other devices.